There has been a recent concern raised regarding the contamination of water supplies by Cryptosporidium oocyts. There was sparked by the outbreak that occurred in Milwaukee. While contamination by any microbial agent is of concern Cryptosporidium has received much attention, in part, because it is a problem for immunocompromised patients such as those with AIDS. Current methods of diagnosing cryptosporidiosis in humans is based on the detection of oocysts in stool. More recently immunofluorescent test have provided increased sensitivity but it is dependent on trained personnel and expensive equipment i.e., fluorescent microscope. The development of a simple, economical highly sensitive bioluminescent immunoassay for the detection and quantification of Cryptosporidium oocysts in both clinical and environmental settings is the subject of this proposal. This is to be accomplished using monoclonal antibodies specific for this organism and a proprietary bioluminescent detection system developed by SeaLite Sciences Inc. The bioluminescent label is based on Aqualite technology, a calcium activated photoprotein which when conjugated with antibodies results in highly sensitive bioluminescent detection reagents that have been successfully applied to a number of clinical assays.